Power transmission system of hybrid electric vehicle

Abstract

A power transmission system of a hybrid electric vehicle may include an input shaft receiving torque of an engine, an output gear, a first planetary gear set disposed on the input shaft and including a first rotation element connected to a first motor/generator, a second rotation element, and a third rotation element connected to the input shaft, a second planetary gear set disposed on the input shaft and including a fourth rotation element connected to a second motor/generator, a fifth rotation element directly connected to the second rotation element and to the output gear, and a sixth rotation element selectively connected to a transmission housing and selectively connected to the first rotation element, and frictional elements selectively connecting two rotation elements of the second planetary gear set, selectively connecting the first rotation element to the sixth rotation element, or selectively connecting the sixth rotation element to the transmission housing.

What is claimed is: 
     
       1. A power transmission system of a hybrid electric vehicle, comprising:
 an input shaft receiving torque of an engine; 
 an output gear outputting changed torque; 
 a first planetary gear set disposed on the input shaft and including:
 a first rotation element connected to a first motor/generator; 
 a second rotation element; and 
 a third rotation element connected to the input shaft; 
 
 a second planetary gear set including:
 a fourth rotation element connected to a second motor/generator; 
 a fifth rotation element continuously connected to the second rotation element and to the output gear; and 
 a sixth rotation element selectively connected to a transmission housing, wherein the sixth rotation element is directly engaged with the first rotation element and wherein the sixth rotation element and the first rotation element are selectively connected; and 
 
 frictional elements selectively connecting two rotation elements of the second planetary gear set, selectively connecting the first rotation element to the sixth rotation element, or selectively connecting the sixth rotation element to the transmission housing. 
 
     
     
       2. The power transmission system of  claim 1 ,
 wherein the first planetary gear set is a single pinion planetary gear set, and includes:
 a first sun gear being the first rotation element; 
 a first planet carrier being the second rotation element; and 
 a first ring gear being the third rotation element, and 
 
 wherein the second planetary gear set is a single pinion planetary gear set, and includes:
 a second sun gear being the fourth rotation element; 
 a second planet carrier being the fifth rotation element; and 
 a second ring gear being the sixth rotation element. 
 
 
     
     
       3. The power transmission system of  claim 1 ,
 wherein the first planetary gear set is a double pinion planetary gear set, and includes:
 a first sun gear being the first rotation element; 
 a first ring gear being the second rotation element; and 
 a first planet carrier being the third rotation element, and 
 
 wherein the second planetary gear set is a single pinion planetary gear set, and includes:
 a second sun gear being the fourth rotation element; 
 a second planet carrier being the fifth rotation element; and 
 a second ring gear being the sixth rotation element. 
 
 
     
     
       4. The power transmission system of  claim 1 , wherein the frictional elements comprise:
 a first clutch selectively connecting two rotation elements of the second planetary gear set; 
 a second clutch selectively connecting the first rotation element to the sixth rotation element; and 
 a first brake selectively connecting the sixth rotation element to the transmission housing. 
 
     
     
       5. The power transmission system of  claim 4 , wherein the first clutch is disposed between the fourth rotation element and the fifth rotation element. 
     
     
       6. The power transmission system of  claim 4 , wherein the first clutch is disposed between the fourth rotation element and the second rotation element. 
     
     
       7. The power transmission of  claim 4 ,
 wherein the first brake is operated at a first EV mode, 
 wherein the first clutch is operated at a second EV mode, 
 wherein the first brake is operated at a first hybrid operating mode, 
 wherein the first clutch is operated at a second hybrid operating mode, 
 wherein the second clutch is operated at a third hybrid operating mode, 
 wherein the second clutch and the first brake are operated at a first engine mode, and 
 wherein the first clutch and the second clutch are operated at a second engine mode. 
 
     
     
       8. The power transmission system of  claim 1 , wherein a third clutch is disposed between the engine and the input shaft. 
     
     
       9. A power transmission system of a hybrid electric vehicle, comprising:
 an input shaft receiving torque of an engine; 
 an output gear outputting changed torque; 
 a first planetary gear set including:
 a first rotation element connected to a first motor/generator; 
 a second rotation element; and 
 a third rotation element connected to the input shaft; 
 
 a second planetary gear set including:
 a fourth rotation element connected to a second motor/generator; 
 a fifth rotation element continuously connected to the second rotation element and to the output gear; and 
 a sixth rotation element selectively connected to a transmission housing, wherein the sixth rotation element is directly engaged with the first rotation element and wherein the sixth rotation element and the first rotation element are selectively connected; 
 
 a first clutch selectively connecting two rotation elements of the second planetary gear set; 
 a second clutch selectively connecting the first rotation element to the sixth rotation element; and 
 a first brake selectively connecting the sixth rotation element to the transmission housing. 
 
     
     
       10. The power transmission system of  claim 9 ,
 wherein the first planetary gear set is a single pinion planetary gear set, and includes:
 a first sun gear being the first rotation element; 
 a first planet carrier being the second rotation element; and 
 a first ring gear being the third rotation element, and 
 
 wherein the second planetary gear set is a single pinion planetary gear set, and includes:
 a second sun gear being the fourth rotation element; 
 a second planet carrier being the fifth rotation element; and 
 a second ring gear being the sixth rotation element. 
 
 
     
     
       11. The power transmission system of  claim 9 ,
 wherein the first planetary gear set is a double pinion planetary gear set, and includes:
 a first sun gear being the first rotation element; 
 a first ring gear being the second rotation element; and 
 a first planet carrier being the third rotation element, and 
 
 wherein the second planetary gear set is a single pinion planetary gear set, and includes:
 a second sun gear being the fourth rotation element; 
 a second planet carrier being the fifth rotation element; and 
 a second ring gear being the sixth rotation element. 
 
 
     
     
       12. The power transmission of  claim 9 ,
 wherein the first brake is operated at a first EV mode, 
 wherein the first clutch is operated at a second EV mode, 
 wherein the first brake is operated at a first hybrid operating mode, 
 wherein the first clutch is operated at a second hybrid operating mode, 
 wherein the second clutch is operated at a third hybrid operating mode, 
 wherein the second clutch and the first brake are operated at a first engine mode, and 
 wherein the first clutch and the second clutch are operated at a second engine mode. 
 
     
     
       13. The power transmission system of  claim 9 , wherein a third clutch is disposed between the engine and the input shaft. 
     
     
       14. The power transmission system of  claim 9 , wherein the first clutch is disposed between the fourth rotation element and the fifth rotation element. 
     
     
       15. The power transmission system of  claim 9 , wherein the first clutch is disposed between the fourth rotation element and the second rotation element. 
     
     
       16. The power transmission system of  claim 4 , wherein the second clutch is mounted between the sixth rotation element and the first rotation element. 
     
     
       17. The power transmission system of  claim 9 , wherein the second clutch is mounted between the sixth rotation element and the first rotation element.